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Journal Articles

Nuclear fuel cycle, nuclear non-proliferation and nuclear security in Japan, 3; Challenges on technologies for nuclear non-proliferation/nuclear security and progressing credibility

Mochiji, Toshiro; Senzaki, Masao*; Tamai, Hiroshi; Iwamoto, Tomonori*; Ishiguro, Yuzuru*; Kitade, Yuta; Sato, Heigo*; Suehiro, Rie*; Taniguchi, Tomihiro*; Fukasawa, Tetsuo*; et al.

Enerugi Rebyu, 40(8), p.56 - 57, 2020/07

Strict application of IAEA safeguards and nuclear security should be implemented for Japan's full-scale nuclear fuel cycle. Based on the knowledge and experience of research and development in the nuclear fuel cycle, nuclear material management, the effective and efficient promotion of new technologies should be promoted with scientific and demonstrative measures to strengthen the world's nuclear non-proliferation and nuclear security. Development or sophistication of new technologies, human resource development, and reinforcement of the international framework are future challenge in the international community.

Journal Articles

Nuclear fuel cycle, nuclear non-proliferation and nuclear security in Japan, 2; Significance of sustainable progress in plutonium-thermal policy and R&D of fast reactor

Mochiji, Toshiro; Senzaki, Masao*; Tamai, Hiroshi; Iwamoto, Tomonori*; Ishiguro, Yuzuru*; Kitade, Yuta; Sato, Heigo*; Suehiro, Rie*; Taniguchi, Tomihiro*; Fukasawa, Tetsuo*; et al.

Enerugi Rebyu, 40(7), p.58 - 59, 2020/06

Japan have promoted the peaceful use of plutonium with the nuclear non-proliferation commitment based on IAEA safeguards agreement and Japan-US nuclear cooperation agreement, as well as ensuring transparency of the policy that Japan has no plutonium without purpose of use. In promoting the nuclear fuel cycle, adherence to those measures and maintaining plutonium utilization by means of plutonium-thermal, and a fast reactor cycle to achieve large-scale and long-term energy supply and environmental improvement, therefore, further research and development is essential.

Journal Articles

Nuclear fuel cycle, nuclear non-proliferation and nuclear security in Japan, 1; Peaceful nuclear use and nuclear non-proliferation

Mochiji, Toshiro; Senzaki, Masao*; Tamai, Hiroshi; Iwamoto, Tomonori*; Ishiguro, Yuzuru*; Kitade, Yuta; Sato, Heigo*; Suehiro, Rie*; Taniguchi, Tomihiro*; Fukasawa, Tetsuo*; et al.

Enerugi Rebyu, 40(6), p.58 - 59, 2020/05

In order to promote the peaceful use of nuclear energy, it is important not only to ensure safety but also to ensure nuclear non-proliferation and nuclear security. Japan has contributed to the international community through strengthening nuclear non-proliferation and nuclear security capabilities with technical and human resource development. However, in the wake of the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, Japan's nuclear power plants have not restarted or plutonium use has not progressed smoothly. Concerns have been shown. Towards appropriate steps of Japan's nuclear fuel cycle policy, such concerns are examined and future efforts are summarized.

Journal Articles

Factors controlling dissolved $$^{137}$$Cs concentrations in east Japanese rivers

Tsuji, Hideki*; Ishii, Yumiko*; Shin, M.*; Taniguchi, Keisuke*; Arai, Hirotsugu*; Kurihara, Momo*; Yasutaka, Tetsuo*; Kuramoto, Takayuki*; Nakanishi, Takahiro; Lee, S*; et al.

Science of the Total Environment, 697, p.134093_1 - 134093_11, 2019/12

 Times Cited Count:3 Percentile:52.23(Environmental Sciences)

To investigate the main factors that control the dissolved radiocesium concentration in river water in the area affected by the Fukushima Daiichi nuclear power plant accident, the correlations between the dissolved $$^{137}$$Cs concentrations at 66 sites normalized to the average $$^{137}$$Cs inventories for the watersheds with the land use, soil components, topography, and water quality factors were assessed. We found that the topographic wetness index is significantly and positively correlated with the normalized dissolved $$^{137}$$Cs concentration. Similar positive correlations have been found for European rivers because wetland areas with boggy organic soils that weakly retain $$^{137}$$Cs are mainly found on plains. However, for small Japanese river watersheds, the building area ratio in the watershed strongly affected the dissolved $$^{137}$$Cs concentration.

Journal Articles

Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

Kurihara, Momo*; Yasutaka, Tetsuo*; Aono, Tatsuo*; Ashikawa, Nobuo*; Ebina, Hiroyuki*; Iijima, Takeshi*; Ishimaru, Kei*; Kanai, Ramon*; Karube, Jinichi*; Konnai, Yae*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 322(2), p.477 - 485, 2019/11

 Times Cited Count:0 Percentile:100(Chemistry, Analytical)

We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the $$^{137}$$Cs results were within $$pm$$2, indicating that the methods were accurate. The relative standard deviations (RSDs) indicating the variability in the results from different laboratories were larger than the RSDs indicating the variability in the results from each separate laboratory.

Journal Articles

Isotope-selective microscale imaging of radioactive Cs without isobaric interferences using sputtered neutral mass spectrometry with two-step resonant ionization employing newly-developed Ti:Sapphire lasers

Sakamoto, Tetsuo*; Morita, Masato*; Kanenari, Keita*; Tomita, Hideki*; Sonnenschein, V.*; Saito, Kosuke*; Ohashi, Masaya*; Kato, Kotaro*; Iguchi, Tetsuo*; Kawai, Toshihide*; et al.

Analytical Sciences, 34(11), p.1265 - 1270, 2018/11

 Times Cited Count:4 Percentile:67.24(Chemistry, Analytical)

Journal Articles

Summary of discussion on AESJ special committee; Study of ensuring safety for near-surface disposal of uranium-bearing waste

Iguchi, Tetsuo*; Hasegawa, Makoto; Takahashi, Kuniaki; Enokido, Yuji*

Dekomisshoningu Giho, (52), p.12 - 19, 2015/09

no abstracts in English

Journal Articles

A Study on fast digital discrimination of neutron and $$gamma$$-ray for improvement neutron emission profile measurement

Uchida, Yuki*; Takada, Eiji*; Fujisaki, Akihiro*; Isobe, Mitsutaka*; Ogawa, Kunihiro*; Shinohara, Koji; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*

Review of Scientific Instruments, 85(11), p.11E118_1 - 11E118_4, 2014/11

 Times Cited Count:4 Percentile:72.58(Instruments & Instrumentation)

Journal Articles

Performance evaluation of a resonance ionization mass spectrometer developed for the FFDL system of fast reactors

Iwata, Yoshihiro; Ito, Chikara; Harano, Hideki*; Iguchi, Tetsuo*

Journal of Nuclear Science and Technology, 51(4), p.465 - 475, 2014/04

 Times Cited Count:3 Percentile:67.77(Nuclear Science & Technology)

To prevent a fuel failure event from becoming a serious radiation accident, sodium-cooled fast reactors are equipped with a system for failed fuel detection and location (FFDL). The FFDL instrument employed in the prototype fast breeder reactor Monju is based on the gas tagging method, in which precise and accurate measurements of krypton and xenon isotope ratios ($$^{78}$$Kr/$$^{80}$$Kr, $$^{82}$$Kr/$$^{80}$$Kr and $$^{126}$$Xe/$$^{129}$$Xe) must be performed in a short time. Burnup measurements also contribute to accurate determination of $$^{82}$$Kr/$$^{80}$$Kr. We have developed a highly sensitive resonance ionization mass spectrometer for the isotopic analyses, which uses resonance ionization of Kr and Xe atoms by a pulsed laser at wavelengths of 216.7 nm and 249.6 nm, respectively. In evaluating the performance of our spectrometer, we find that systematic errors caused by isotope shifts can be reduced to negligible levels, and that statistical errors of 3% at a nuclide concentration of 7 ppt can be achieved with a single measurement time of about 40 minutes for each Kr and Xe isotope ratio. This means that, within one hour, about 200 fuel assemblies can be individually identified with a probability of 99%, verifying the applicability of our spectrometer to the FFDL system of fast reactors.

Journal Articles

Fast neutron detection under intense $$gamma$$-ray fields with novel nuclear emulsion technique

Ishihara, Kohei*; Takagi, Keisuke*; Minato, Haruna*; Kawarabayashi, Jun*; Tomita, Hideki*; Maeda, Shigetaka; Naka, Tatsuhiro*; Morishima, Kunihiro*; Nakano, Toshiyuki*; Nakamura, Mitsuhiro*; et al.

Radiation Measurements, 55, p.79 - 82, 2013/08

 Times Cited Count:1 Percentile:86.47(Nuclear Science & Technology)

In order to measure the neutron under a condition of high intensity of $$gamma$$-ray background, we made new nuclear emulsion based on non-sensitized OPERA emulsion which had small AgBr grain size (AgBr grain size of 60, 90 and 160 nm). The sensitivity of this new emulsion, which was a correlation between stopping power and grain density, was estimated experimentally by irradiating neutrons with several energies. We also simulated the response to $$gamma$$-ray induced electrons and compared with some experimental results by using $$^{60}$$Co $$gamma$$ source. The results showed that there might be a threshold energy deposited in one AgBr grain under which it was impossible to develop. We estimated efficiency to the $$gamma$$-ray and the neutron with this obtained response of the new emulsion.

Journal Articles

A New unfolding code combined maximum entropy and maximum likelihood for neutron spectrum measurement

Maeda, Shigetaka; Iguchi, Tetsuo*

Journal of Nuclear Science and Technology, 50(4), p.381 - 386, 2013/03

 Times Cited Count:1 Percentile:86.47(Nuclear Science & Technology)

We present a new spectrum unfolding code, the Maximum Entropy and Maximum Likelihood Unfolding Code (MEALU), based on the maximum likelihood method combined with the maximum entropy method, which can determine a neutron spectrum without requiring an initial guess spectrum. The Normal or Poisson distributions can be used for the statistical distribution. MEALU can treat full covariance data for a measured detector response and response function. The algorithm was verified through an analysis of mock-up data and its performance was checked by applying it to measured data. The results for measured data from the experimental fast reactor Joyo also were compared with those obtained by the conventional J-log method for neutron spectrum adjustment. It was found that MEALU has potential advantages over conventional methods with regard to preparation of a priori information and error estimation.

Journal Articles

Development of neutron measurement in intense $$gamma$$ field using new type of nuclear emulsion

Kawarabayashi, Jun*; Ishihara, Kohei*; Takagi, Keisuke*; Tomita, Hideki*; Iguchi, Tetsuo*; Naka, Tatsuhiro*; Morishima, Kunihiro*; Maeda, Shigetaka

Journal of ASTM International (Internet), 9(3), 5 Pages, 2012/03

In order to measure the neutron from a spent fuel assembly in fast breeder reactor precisely, we made new nuclear emulsion based on non-sensitized OPERA film with AgBr grain size of 60, 90 and 160 nm. The efficiency for $$^{252}$$Cf neutron of the new emulsion was calculated to be 0.7$$times$$10$$^{-4}$$ which energy ranged from 0.3 to 2 MeV that agrees with preliminary estimated value from experimental results. The sensitivity of the new emulsion was also estimated experimentally by irradiating 565 KeV and 14 MeV neutrons and found that the emulsion with the AgBr grain size of 60 nm showed the lowest sensitivity among these three emulsions but still had enough sensitivity for proton. Also, there was a suggestion from the experimental data that there was a threshold LET of 15 KeV/$$mu$$m for our new emulsion below which no silver cluster was developed. Further development of the response of nuclear emulsion with a few tens of nano-meter AgBr size is next step of this study.

Journal Articles

Present status and problems of neutron spectrum unfolding method in reactor dosimetry

Maeda, Shigetaka; Iguchi, Tetsuo*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 10(2), p.63 - 75, 2011/06

Neutron spectrum unfolding is a widely applied technique to characterize neutron fields for various types of reactor dosimetry, where the neutron spectrum is derived from integral measured data such as multiple-foil activation rates, moderated neutron detector counts, etc. A lot of spectrum unfolding codes have been developed so far and their performances compared to each other. However, standardized metrology for neutron spectrum unfolding is not satisfactorily established yet from the viewpoint of adequate selection and usage of unfolding codes, response function database and input data set preparation. This article reviews the present status on the neutron spectrum unfolding techniques mainly related to the reactor dosimetry with activation foils and discusses the validity of the solution spectra obtained from different kinds of unfolding codes under a typical fast reactor neutron field. The results show that the solution spectrum strongly depends on a guess spectrum required to the input data as well as the theoretical assumption in each unfolding code. The issues to improve the accuracy of reactor dosimetry are summarized on the ${it a priori}$ input spectrum, nuclear database and the standardization of unfolding procedure, respectively.

Journal Articles

High sensitive and reliable FFDL technique for SFR using laser resonance ionization mass spectrometry

Ito, Chikara; Iwata, Yoshihiro; Harano, Hideki*; Iguchi, Tetsuo*; Aoyama, Takafumi

Transactions of the American Nuclear Society, 102(1), p.416 - 417, 2010/06

no abstracts in English

Journal Articles

Development of highly sensitive sodium leak detection technology by means of laser for fast reactor (Fundamental experiments for atomization and resonance ionization of sodium and design of prototype sodium detection system)

Aoyama, Takafumi; Ito, Chikara; Okazaki, Koki*; Harano, Hideki*; Watanabe, Kenichi*; Iguchi, Tetsuo*

Nippon Kikai Gakkai Rombunshu, B, 75(751), p.468 - 470, 2009/03

no abstracts in English

Journal Articles

Multi-scattering time-of-flight neutron spectrometer for deuterium to tritium fuel ratio measurement in fusion experimental reactors

Asai, Keisuke*; Yukawa, Kyohei*; Iguchi, Tetsuo*; Naoi, Norihiro*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Yamauchi, Michinori*; Konno, Chikara

Fusion Engineering and Design, 83(10-12), p.1818 - 1821, 2008/12

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

The fuel ratio in a DT burning plasma can be derived from the intensity ratio of DD/DT neutrons, and detecting a trace of DD neutrons in the DT burning plasma is a key issue. A new type of neutron spectrometer is proposed to monitor the fuel ratio in the core of the ITER plasma. The system based on a conventional time-of-flight method consists of a water cell as a neutron scattering material and tens of scintillator pairs arranged around the first scintillator in a corn shape. We call it a multi-scattering time-of-flight neutron spectrometer (MS-TOF). A trial experiment was conducted for the prototype MS-TOF system with a DT neutron beam (20-mm diameter) at the Fusion Neutronics Source (FNS), Japan Atomic Energy Agency. The experimental results show that the DD and DT neutron peaks are clearly observed, and the experiment has successfully demonstrated the feasibility of the MS-TOF concept for detecting trace-DD neutrons within a DT neutron beam extracted from a DT burn plasma.

Journal Articles

Development of sodium leak detection technology using laser resonance ionization mass spectrometry

Aoyama, Takafumi; Ito, Chikara; Okazaki, Koki; Harano, Hideki; Watanabe, Kenichi*; Iguchi, Tetsuo*

Journal of Nuclear Science and Technology, 45(Suppl.6), p.43 - 50, 2008/09

 Times Cited Count:1 Percentile:88.43(Nuclear Science & Technology)

no abstracts in English

Journal Articles

X-ray magnetic circular dichroism and photoemission studies of ferromagnetism in CaMn$$_{1-x}$$Ru$$_{x}$$O$$_{3}$$ thin films

Terai, Kota*; Yoshii, Kenji; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Owada, Kenji; Inami, Toshiya; Okane, Tetsuo; Arita, Masashi*; Shimada, Kenya*; et al.

Physical Review B, 77(11), p.115128_1 - 115128_6, 2008/03

 Times Cited Count:12 Percentile:48.2(Materials Science, Multidisciplinary)

Journal Articles

Electronic structure and magnetism of CaMn$$_{1-x}$$Ru$$_{x}$$O$$_{3}$$ thin films

Terai, Kota; Yoshii, Kenji; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Owada, Kenji; Inami, Toshiya; Okane, Tetsuo; Arita, Masashi*; Shimada, Kenya*; et al.

Journal of Magnetism and Magnetic Materials, 310(2, Part2), p.1070 - 1072, 2007/03

We have studied the electronic and magnetic properties of epitaxially grown CaMn$$_{1-x}$$Ru$$_{x}$$O$$_{3}$$ (x = 1.0, 0.5) thin films by X-ray magnetic circular dichroism (XMCD) and hard X-ray photoemission spectroscopy (HXPES). The XMCD studies indicated that the spin moments of Mn and Ru are aligned in the opposite directions. The HXPES spectra indicated the Ru 4d states at around the Fermi edge (E$$_{F}$$) and the Mn 3d states below E$$_{F}$$. From these results, we propose that the localized Mn 3d t$$_{2g}$$ states and the itinerant Ru 4d t$$_{2g}$$ band are antiferromagnetically coupled and give rise to ferromagnetism, in analogy with the mechanism proposed for the double perovskite oxides such as Sr$$_{2}$$FeMoO$$_{6}$$.

Journal Articles

Novel concept of time-of-flight neutron spectrometer for measurement of the D/T burning ratio in the ITER

Asai, Keisuke*; Naoi, Norihiro*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Nishitani, Takeo

Review of Scientific Instruments, 77(10), p.10E721_1 - 10E721_3, 2006/10

 Times Cited Count:3 Percentile:78.07(Instruments & Instrumentation)

A time-of-flight (TOF) neutron spectrometer is one of the candidates of the measurement of the D/T burning ratio in ITER. In the ITER high power experiments, the TOF system would suffer from high event rate or accidental counts due to high radiation intensities, which can be one of background sources for DD neutron measurement. We propose a new neutron spectrometer to apply to the measurement of the D/T burning ratio in the ITER high power operation region. This system is based on the conventional double crystal TOF method and consists of a water cell and several pairs of scintillators. A water cell is inserted before the first scintillator of the TOF system and acts as a radiator or neutron scattering material. Because DD neutrons have a larger cross section of elastic scattering with hydrogen than DT neutrons, the elastic scattering in the radiator enhances the relative ratio of DD/DT intensity by about 3 times before entering the TOF system. The enhancement of the relative intensity of DD neutrons makes the detection of DD neutrons easier. The feasibility of this method as a neutron spectrometer and the basic performances of this system have been verified through a preliminary experiment using a DT neutron beam (20 mm$$phi$$) at the Fusion Neutronics Source, Japan Atomic Energy Agency.

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